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improved LZ4HC_reverseCountPattern() :

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works for any repetitive pattern of length 1, 2 or 4 (but not 3!)
works for any endianess
This commit is contained in:
Yann Collet 2017-11-07 11:05:48 -08:00
parent a004c1fbee
commit 7130bfe573
1 changed files with 7 additions and 3 deletions
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10
lib/lz4hc.c
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@ -161,17 +161,21 @@ static unsigned LZ4HC_countPattern(const BYTE* ip, const BYTE* const iEnd, U32 c
return (unsigned)(ip - iStart);
}
/* LZ4HC_reverseCountPattern() :
* pattern must be a sample of repetitive pattern of length 1, 2 or 4 (but not 3!)
* read using natural platform endianess */
static unsigned LZ4HC_reverseCountPattern(const BYTE* ip, const BYTE* const iLow, U32 pattern)
{
const BYTE* const iStart = ip;
while (likely(ip>=iLow+4)) {
while (likely(ip >= iLow+4)) {
if (LZ4_read32(ip-4) != pattern) break;
ip -= 4;
}
while (likely(ip>iLow)) {
if (ip[-1] != (BYTE)pattern) break;
ip--;
const BYTE* bytePtr = (const BYTE*)(&pattern) + 3; /* works for any endianess */
if (ip[-1] != *bytePtr) break;
ip--; bytePtr--;
}
return (unsigned)(iStart - ip);